Academic literature on the topic 'High-order X-FEM'
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Journal articles on the topic "High-order X-FEM"
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Legrain, G., N. Chevaugeon, and K. Dréau. "High order X-FEM and levelsets for complex microstructures: Uncoupling geometry and approximation." Computer Methods in Applied Mechanics and Engineering 241-244 (October 2012): 172–89. http://dx.doi.org/10.1016/j.cma.2012.06.001.
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Sawada, Tomohiro, and Akira Tezuka. "High-order gaussian quadrature in X-FEM with the lagrange-multiplier for fluid-structure coupling." International Journal for Numerical Methods in Fluids 64, no. 10-12 (November 25, 2010): 1219–39. http://dx.doi.org/10.1002/fld.2343.
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Wu, Shaoqi, Olivier Dazel, Gwénaël Gabard, and Grégory Legrain. "High-order X-FEM for the simulation of sound absorbing poro-elastic materials with coupling interfaces." Journal of Sound and Vibration 510 (October 2021): 116262. http://dx.doi.org/10.1016/j.jsv.2021.116262.
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Rezikyan, Aram, Zechariah J. Jibben, Bryan A. Rock, Gongpu Zhao, Franz A. M. Koeck, Robert F. Nemanich, and Michael M. J. Treacy. "Speckle Suppression by Decoherence in Fluctuation Electron Microscopy." Microscopy and Microanalysis 21, no. 6 (September 18, 2015): 1455–74. http://dx.doi.org/10.1017/s1431927615015135.
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AbstractWe compare experimental fluctuation electron microscopy (FEM) speckle data with electron diffraction simulations for thin amorphous carbon and silicon samples. We find that the experimental speckle intensity variance is generally more than an order of magnitude lower than kinematical scattering theory predicts for spatially coherent illumination.We hypothesize that decoherence, which randomizes the phase relationship between scattered waves, is responsible for the anomaly. Specifically,displacement decoherencecan contribute strongly to speckle suppression, particularly at higher beam energies. Displacement decoherence arises when the local structure is rearranged significantly by interactions with the beam during the exposure. Such motions cause diffraction speckle to twinkle, some of it at observable time scales.We also find that the continuous random network model of amorphous silicon can explain the experimental variance data if displacement decoherence and multiple scattering is included in the modeling. This may resolve the longstanding discrepancy between X-ray and electron diffraction studies of radial distribution functions, and conclusions reached from previous FEM studies.Decoherence likely affects all quantitative electron imaging and diffraction studies. It likely contributes to the so-called Stobbs factor, where high-resolution atomic-column image intensities are anomalously lower than predicted by a similar factor to that observed here.
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Watthewaduge, Gayan, and Berker Bilgin. "Sizing of the Motor Geometry for an Electric Aircraft Propulsion Switched Reluctance Machine Using a Reluctance Mesh-Based Magnetic Equivalent Circuit." Machines 11, no. 1 (January 4, 2023): 59. http://dx.doi.org/10.3390/machines11010059.
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The switched reluctance motor (SRM) is a promising candidate for electric propulsion systems. In the design process of an SRM, the motor geometry needs to be determined. Using the finite element method (FEM) might be time-consuming for the sizing of the motor geometry. As an alternative, electromagnetic models based on a magnetic equivalent circuit (MEC) can be utilized for the sizing of an SRM. MEC models require fewer computational resources and can help determine the electromagnetic performance with reasonable accuracy. Using the conventional MEC method for SRM sizing might be challenging since the flux pattern inside the motor should be changed for different motor dimensions. In order to address this challenge, this paper applies a reluctance mesh-based MEC technique to determine the geometry of a three-phase 12/16 SRM for a high-lift motor in the NASA Maxwell X-57 electric aircraft. A comprehensive reluctance mesh-based MEC model is developed for this purpose. Both the static and dynamic characteristics of the SRM geometry are evaluated using the reluctance mesh-based MEC method. The determined geometry is verified using the results computed from FEM.
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Hattali, M. L., Stéphane Valette, François Ropital, N. Mesrati, and Daniel Treheux. "Fem Calculations and Experimental Determination of Residual Stresses in Alumina/Nickel Alloy Joints. Optimization of Fabrication Parameters." Advanced Materials Research 89-91 (January 2010): 238–43. http://dx.doi.org/10.4028/www.scientific.net/amr.89-91.238.
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The study relates to joints fabricated by solid state bonding between alumina and nickel alloy HAYNESTM214®, using an intermediate nickel metallic foil. Experimentally, damages and cracks often are observed close to the metal/ceramics interface. Consequently, the residual stresses distributions in the specimen were characterized experimentally using X-ray diffraction (XRD) and indentation techniques and predicted by Finite Element Analysis (FEA) calculations using an elastic-plastic-creep model. We demonstrate that a good correlation between FEA calculations and experimental results is obtained. Then, the effect of elaboration and geometrical parameters has been studied in order to minimize the residual stresses in alumina close to the metal-ceramics interface. However, the Al2O3/Ni/HAYNESTM214® system always leads to high residual stresses. To solve this problem, we show that the use of a multi-layer Cu/Ni/Cu joint, associated with the Direct Copper Bonding method (DCB), by pre-oxidation of copper, allows reducing significantly the tensile residual stresses in ceramics.
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Kurita, Masanori, Makoto Sato, Ikuo Ihara, and Akira Saito. "Residual Stress Distribution of Ceramic-Metal Joint." Advances in X-ray Analysis 33 (1989): 353–62. http://dx.doi.org/10.1154/s0376030800019765.
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AbstractCeramics are sometimes bonded to ductile metals in order to make up for their brittle behavior for industrial use. The residual stress will be induced in ceramics bonded to metals at high temeprature, and it has a strong influence on the strength of ceramic-metal joints. A silicon nitride plate was bonded to a carbon steel plate by brazing to a copper sheet sandwiched between the two materials. The residual stress distribution of the joint specimen was determined by x-ray diffraction using the Gaussian curve method. The measured residual stress distribution almost agreed with that calculated by the three-dimensional thermoelastoplastic stress analysis using FEM, but differed remarkably from that calculated by the two-dimensional stress analysis. This is because a stress concentration occurs at the ceramic-metal interface and the stress distributes three - dimensionally. The stress σx in the axial direction on the surface of the specimen takes maximum values at the center and the edge of the interface.
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Guo, Zixu, Ziyuan Song, Dawei Huang, and Xiaojun Yan. "A High-Temperature Digital Image Correlation Method and its Application on Strain Measurement of Film Cooling Holes." Journal of Multiscale Modelling 12, no. 02 (June 2021): 2150003. http://dx.doi.org/10.1142/s1756973721500037.
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In this paper, a digital image correlation (DIC) method is developed and applied on film cooling holes in the submillimeter scale in high temperature. Compared with the traditional DIC method, the speckle patterning method and the optical system are improved. In detail, a kind of high temperature-resistant black paint is selected as the basecoat, and the white ZrO2 particles are evenly distributed on the specimen using high-pressure splashing method. Besides, to eliminate the radiation effect of the high-temperature specimen, the blue light source is used to illuminate the specimen, and the optical bandpass filter is placed in front of the camera to allow the blue light passing. In order to verify the DIC method, the strain measurement on a specimen with single skew hole is performed. The relative error in high temperature of the maximum strain between the measurement results and the numerical simulation results given by the finite element method (FEM) is 12%. The strain concentration factor of the single skew hole is measured as 1.83. Finally, the developed method is applied to the strain measurement of the structure with multiple film cooling holes in 870°C. The X-shape strain distribution can be observed at the hole with maximum stress, which suggests that the strain field of multiple holes has coupling effect. In addition, the strain concentration factor of multiple film cooling holes increases to 2.34.
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Britez, C., J. Gadea, M. Carvalho, and P. Helene. "Hormigón y Hormigonado de Cimentación con Hormigón Autocompactante y de Elevadas Prestaciones (70 MPa)." Revista ALCONPAT 6, no. 1 (January 30, 2016): 28–40. http://dx.doi.org/10.21041/ra.v6i1.113.
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Hormigón y Hormigonado de Cimentación con Hormigón Autocompactante y de Elevadas Prestaciones (70 MPa)RESUMENEl Edificio Comercial Brookfield Century Plaza, localizado en Alphaville, São Paulo, Brasil, fue diseñado para ser sostenido por dos grandes bloques de hormigón. Un hormigón de alta resistencia (70 MPa) y SCC auto compactante fue desarrollado para estos dos bloques masivos de fundación (cada un mide 28.4mx 18.6m por 4.5m de altura). Un modelo numérico utilizando un software FEM fue desarrollado para predecir la ganancia térmica de hidratación de diferentes capas de hormigonado con el fin de establecer el procedimiento más adecuado para cumplir con los requisitos de tiempo y de la construcción, sin que aparezcan fisuras. Fueron establecidos y supervisados procedimientos para controlar la producción de concreto en la empresa productora de concretos y aplicarlo en el sitio de construcción. Finalmente, la temperatura interna del concreto se registró para permitir una mejor calibración del modelo.Palabras clave: concreto de alta resistencia, concreto autocompactante, concreto masivo, producción de concreto refrigerado. Material and Casting Methodology for SCC and HPC (70 MPa) Concrete Foundation BlocksABSTRACTThe Brookfield Century Plaza Commercial Building, located in Alphaville District, in São Paulo, Brazil, was designed to be supported by two direct foundation concrete blocks. A high strength (70 MPa), self-compacting concrete SCC was developed for these two massive foundation blocks (each one measures 28.4m x 18.6m by 4.5m, high). A numerical model by employing a FEM software was developed to predict the thermal hydration gain of different casting procedures, in order to establish the most appropriate one to meet the construction and schedule requirements without cracks. Directions to control concrete production at mixing plant and placing at construction site were established as well as supervised. Finally, internal concrete temperatures were recorded to enable a better model calibration.Keywords: High strength concrete, self-compacting concrete, concrete modeling, refrigerated concrete production. Concreto e Concretagem de Blocos de Fundação em Concreto Autoadensável e de Alta Resistência (70 MPa)RESUMOO Edifício Comercial Brookfield Century Plaza, localizado em Alphaville, São Paulo, Brasil, foi projetado para ser apoiado em dois grandes blocos de concreto. Um concreto de alta resistência (70 MPa) e SCC auto adensável foi desenvolvido para estes dois blocos maciços de fundação (cada um medindo 28.4m x 18.6m por 4.5m de altura). Um modelo numérico empregando um software FEM foi desenvolvido para prever o ganho de hidratação térmica de diferentes camadas de concretagem, a fim de estabelecer o procedimento mais adequado para cumprir o cronograma e os requisitos de construção, sem fissurar. Diretrizes para controlar a produção do concreto na empresa de serviços de concretagem e procedimentos de como aplicá-lo no canteiro de obras foram estabelecidas e supervisionadas. Finalmente, as temperaturas internas do concreto foram registradas para permitir uma melhor calibração do modelo.Palavras-chave: Concreto de alta resistência, concreto auto adensável, modelagem de concreto massa, produção de concreto refrigerado.
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Cannillo, Valeria, Tiziano Manfredini, M. Montorsi, Cristina Siligardi, and A. Sola. "Experimental Characterization and Computational Simulation of Glass-Alumina Functionally Graded Surfaces." Materials Science Forum 492-493 (August 2005): 647–52. http://dx.doi.org/10.4028/www.scientific.net/msf.492-493.647.
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Functionally graded materials are a new and attractive class of materials incorporating an engineered spatial variation in composition and/or microstructure: this idea has immediately revealed successful since it allows to reach peculiar mechanical properties such as resistance to wear and contact damage. As a matter of fact, the final behaviour of a Functionally Graded Material is mainly influenced by its graded composition and/or microstructure. Therefore a good fabrication technique should provide a high control and reproducibility of the spatial variation in composition and/or microstructure; on the other hand, a reliable model should take into account the gradient in order to accurately predict the final behaviour of a Functionally Graded Material. The present study is focused on glass-alumina FGMs: the compositional variation, which occurs along only one direction, has been realized through percolation of a molten glass into a bulk polycrystalline alumina. The resulting Functionally Graded Coatings have been carefully characterized through Scanning Electron Microscopy, X-ray diffraction, classical mechanical tests and analysis. Moreover, their behaviour has been modeled by means of a microstructure-based FEM method. A great attention has been paid to the validation of the computational model on the basis of the experimental data. Furthermore, the experimental and the computational approaches have been combined in order to define the correlation between fabrication parameters, such as time and temperature, and resulting gradients in composition and microstructure as well as related performances. Since changes in material properties can be easily evaluated, the resulting model may be useful to simulate the material response to a given thermo-mechanical loading and to tailor the gradient as a function of the specific application.
Dissertations / Theses on the topic "High-order X-FEM"
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Wu, Shaoqi. "Éléments finis étendus pour la modélisation des interfaces en vibro-acoustique dissipative." Thesis, Ecole centrale de Nantes, 2022. http://www.theses.fr/2022ECDN0041.
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Le bruit est aujourd’hui omniprésent dans notre société, ce qui incite à en diminuer les impacts sur la santé. Grâce à leur légèreté et à leur flexibilité en termes de conception, les ensembles d’absorption acoustique constitués de matériaux poreux pourraient occuper une position centrale parmi les approches visant à réduire le bruit. Notre intérêt se porte sur les systèmes d’absorption comportant de multiples couches avec de grandes disparités d’épaisseur (de quelques millimètres à plusieurs mètres), et de géométries potentiellement complexes. Notre objectif est d’élaborer des méthodes numériques plus efficaces que la méthodedes éléments finis (FEM) pour prédire le comportement vibroacoustique de ces systèmes. Sur la base de la méthode des éléments finis étendus (X-FEM), des stratégies d’enrichissement et de discrétisation sont proposées pour le couplages de milieux poreuximpliquant des équations de Biot. Des formulations variationnelles stables et robustes sont proposées pour prendre en compte l’effetdes couches poreuses minces. Il est démontré que nos approches sont capables de réduire considérablement le temps de pré-traitement et de résolution tout en maintenant le niveau de précision par rapport aux éléments finis classiquesNoise is nowadays omnipresent in our society, which encourages us to reduce its impact on health. Thanks to their design flexibility and lightness, sound absorbing packages made of porous materials might hold a pivotal position among noise reduction approaches. Our prime interest is in sound packages which have multiple layers with significant thickness disparity ranging from several meters to millimeters and potentiallycomplex geometries. We aim at elaborating on more efficient numerical methods to identify and predict the vibroacoustic behaviour of suchpackages compared to the classical Finite Element Method (FEM). Based on the eXtended Finite Element Method (X-FEM), enrichment and discretization strategies are developed to couple porous media involving mixed Biot’s equations. Stable and robust variational formulations are proposed to represent the acoustic effects of thin porous layers. Our approaches are demonstrated to be capable of reducing considerably the preprocessing and resolution times while maintaining the accuracy level in comparison with classical FEM
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Muduli, Pranaba Kishor. "Ferromagnetic thin films of Fe and Fe 3 Si on low-symmetric GaAs(113)A substrates." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2006. http://dx.doi.org/10.18452/15473.
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In dieser Arbeit werden das Wachstum mittels Molekularstrahlepitaxie und die Eigenschaften der Ferromagneten Fe und Fe_3Si auf niedrig-symmetirschen GaAs(113)A-Substraten studiert. Drei wichtige Aspekte werden untersucht: (i) Wachstum und strukturelle Charakterisierung, (ii) magnetische Eigenschaften und (iii) Magnetotransporteigenschaften der Fe und Fe_3Si Schichten auf GaAs(113)A-Substraten. Das Wachstum der Fe- und Fe_3Si-Schichten wurde bei einer Wachstumstemperatur von = bzw. 250 °C optimiert. Bei diesen Wachstumstemperaturen zeigen die Schichten eine hohe Kristallperfektion und glatte Grenz- und Oberflächen analog zu [001]-orientierten Schichten. Weiterhin wurde die Stabilität der Fe_(3+x)Si_(1-x) Phase über einen weiten Kompositionsbereich innerhalb der Fe_3Si-Stoichiometry demonstriert. Die Abhängigkeit der magnetischen Anisotropie innerhalb der Schichtebene von der Schichtdicke weist zwei Bereiche auf: einen Beresich mit dominanter uniaxialer Anisotropie für Fe-Schichten = 70 MLs. Weiterhin wird eine magnetische Anisotropie senkrecht zur Schichtebene in sehr dünnen Schichten gefunden. Der Grenzflächenbeitrag sowohl der uniaxialen als auch der senkrechten Anisotropiekonstanten, die aus der Dickenabhängigkeit bestimmt wurden, sind unabhängig von der [113]-Orientierung und eine inhärente Eigenschaft der Fe/GaAs-Grenzfläche. Die anisotrope Bindungskonfiguration zwischen den Fe und den As- oder Ga-Atomen an der Grenzfläche wird als Ursache für die uniaxiale magnetische Anisotropie betrachtet. Die magnetische Anisotropie der Fe_3Si-Schichten auf GaAs(113)A-Substraten zeigt ein komplexe Abhängigkeit von der Wachstumsbedingungen und der Komposition der Schichten. In den Magnetotransportuntersuchungen tritt sowohl in Fe(113)- als auch in Fe_3Si(113)-Schichten eine antisymmetrische Komponente (ASC) im planaren Hall-Effekt (PHE) auf. Ein phänomenologisches Modell, dass auf der Kristallsymmetrie basiert, liefert ein gute Beschreibung sowohl der ASC im PHE als auch des symmetrischen, anisotropen Magnetowiderstandes. Das Modell zeigt, dass die beobachtete ASC als Hall-Effekt zweiter Ordnung beschreiben werden kann.In this work, the molecular-beam epitaxial growth and properties of ferromagnets, namely Fe and Fe_3Si are studied on low-symmetric GaAs(113)A substrates. Three important aspects are investigated: (i) growth and structural characterization, (ii) magnetic properties, and (iii) magnetotransport properties of Fe and Fe_3Si films on GaAs(113)A substrates. The growth of Fe and Fe_3Si films is optimized at growth temperatures of 0 and 250 degree Celsius, respectively, where the layers exhibit high crystal quality and a smooth interface/surface similar to the [001]-oriented films. The stability of Fe_(3+x)Si_(1-x) phase over a range of composition around the Fe_3Si stoichiometry is also demonstrated. The evolution of the in-plane magnetic anisotropy with film thickness exhibits two regions: a uniaxial magnetic anisotropy (UMA) for Fe film thicknesses = 70 MLs. The existence of an out-of-plane perpendicular magnetic anisotropy is also detected in ultrathin Fe films. The interfacial contribution of both the uniaxial and the perpendicular anisotropy constants, derived from the thickness-dependent study, are found to be independent of the [113] orientation and are hence an inherent property of the Fe/GaAs interface. The origin of the UMA is attributed to anisotropic bonding between Fe and As or Ga at the interface, similarly to Fe/GaAs(001). The magnetic anisotropy in Fe_3Si on GaAs(113)A exhibits a complex dependence on the growth conditions and composition. Magnetotransport measurements of both Fe(113) and Fe_3Si(113) films shows the striking appearance of an antisymmetric component (ASC) in the planar Hall effect (PHE). A phenomenological model based on the symmetry of the crystal provides a good explanation to both the ASC in the PHE as well as the symmetric anisotropic magnetoresistance. The model shows that the observed ASC component can be ascribed to a second-order Hall effect.
Book chapters on the topic "High-order X-FEM"
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Oliver Mnisi, Bhila, Evans Moseti Benecha, and Meriam Malebo Tibane. "Computational Study of A15 Ru-Based Alloys for High-Temperature Structural Applications." In Ruthenium - An Element Loved by Researchers. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.96578.
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The structural, magnetic, electronic and elastic properties of A15 X3Ru (X = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) binary alloys are investigated using first-principles density functional theory (DFT) methods. Ru-based alloys have attracted remarkable research interest due to their unique properties, which make them suitable for high-temperature structural applications. In this chapter, the properties of several A15 Ru-based alloys are investigated in order to select the best suitable alloy/s for aerospace application. Heats of formation are calculated to determine the thermodynamic stability of the materials. Knowledge of the values of elastic constants is essential for understanding the mechanical properties of the materials. From our calculated elastic constants, the bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, melting temperature, anisotropic factor and the ratio B/G are determined. The electronic density of states are calculated and discussed. Lastly, the magnetic properties of A15 X3Ru alloys are studied. Thermodynamically stable Mn3Ru possesses high-magnetic moment compared to other X3Ru alloys, these results could pave way to experimental realization (synthesis) of Mn3Ru material.
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Menino, Regina, and Daniel Murta. "The Insects as a Workforce for Organic Fertilizers Production – Insect Frass." In Organic Fertilizers [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.100144.
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Following the evolution of composting technology, the process of digestion of a biological substrate by insects (entomocomposting) represents the last stage; however, from its initial context of producing an organic fertilizer, the role of entomocomposting has been imposing itself (due to increasing demographic pressure) mainly in the safe disposal of organic waste (in rampant growth) and in the breeding of insects for food and feed, for the sake of food security. Both these last goals converge in the first, as the safest disposal of the compost is its use as organic fertilizer; but the organic substrates are of a diversified nature, as are the species of insects which have already proved themselves in entomocomposting; hence, for each of the purposes in view, the choice is vast and, in the same way, the entomocompost composition is wide-ranging. Furthermore, various types of organic substrates, in addition to a microbial flora with symbiotic effects, may sometimes be able to transmit to the frass a harmful load of heavy metals and/or, depending on the composting insect agents, the presence of microorganisms harmful to crops and to humans and animals; in these situations, the former should be encouraged, and the latter counteracted through appropriate composting technology. Directives and legislation in this area, if properly considered, constitute a fundamental basis for ensuring the appropriate use of this particular kind of organic fertilizer. Apart from the production of insects for food and feed, where the choice of which insect is determined at the outset, the preference for the insect to be used in entomocomposting should be considered according to its proficiency in biological digestion of the organic substrates available for this purpose and the fertilizing quality of the frass produced. Although a multitude of species have been evaluated, to date, for the digestion of organic substrates, most have been used in assessing their specific potential for certain functionalities of frass related to crop nutrition and health, but there are few which, either by prolificacy, proficiency or rapidity in digesting substrates, exhibit capacity to compete in rural environment; nevertheless, new species could be evaluated in the framework of the research of competitors for entomocomposting of all or each substrate type and for each of the main anticipated objectives, meanwhile, genetic improvement to obtain new strains specialized for different organic substrates has already started to take its first steps. In addition to the binomial “insect x substrate” the composting technology constitutes the third fundamental factor for the efficiency of the process. Insects use as a composting agent has been suggested several decades ago, but it was only in the last decade that this process grown from the garden to the factory. Within rural areas, entomocomposting could play a key role within a circular economy, where recycling and reusing potentially polluting wastes safely returns to the land the enduring fertility that enables the sustained production that generated them, requiring no particularly upscale installations, equipment or technical training; it can, therefore, be adapted to any size of agricultural holding, from smallholdings to large industrial holdings, on the other hand, and in order to obtain a controlled production and high quality entomocompost, it is needed to implement industrial technologies and the composting unit can achieve a very high production per square meter, comparing with traditional composting methods. However, whether from the perspective of agriculture, livestock or forestry, the production of waste for entomocomposting always falls far short of the necessary scale, and therefore always requiring the use of biodigested organic waste from agricultural industries, provided that the necessary precautions are taken; in any case, it always constitutes added value, due to the products it generates, in addition to the inestimable value of the productive disposal of potentially polluting products. Despite all the advantages mentioned above, the controversy over the organic vs. mineral fertilizer option persists, often fuelled by myths on both sides, but the successes already achieved with insect entomocomposts, such as the black soldier fly (Hermetia illucens L.) or the mealworm (Tenebrio molitor L.), in field trials, which are gradually adding up, anticipate an important role for insects in safeguarding global food and environmental security.
Conference papers on the topic "High-order X-FEM"
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Bousquet, Amaury, Stéphane Marie, and Philippe Bompard. "Cleavage Dynamic Propagation Analysis in a Nuclear Reactor Pressure Vessel Steel Using a High-Speed Camera." In ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78169.
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Initiation stage of cracks is considered as a key issue, but more and more component integrity analyses investigate the crack propagation and arrest possibility. This study deals with physical mechanisms of cleavage crack propagation and numerical computations related to brittle fracture. Dynamic effects, involved in unstable cleavage crack propagation, have to be taken into account to properly depict brittle crack propagation, arrest and possible propagation re-initiation events. Experiments were carried out on thin CT specimens made of 16MND5 PWR vessel steel at five temperatures (−150°C, −125°C, −100°C, −75°C, −50°C). In addition to standard crack gages, an innovative experimental technique has been used to determine crack propagation. By the means of developments on the experimental protocol (improvements of isolation and airtightness of the thermal chamber, optimization of the experimental protocol to eliminate ice in the thermal chamber and in order to have a good acquisition quality), use of a high-speed framing camera was made possible to measure crack propagation on a CT mirror polished surface. This optical device, combined with this optimized experimental process, has allowed the study of straight and branching crack paths with high accuracy. The framing camera (520 000 fps up to 1 100 000 fps) has allowed to have a very accurate estimation of crack speed even up to 1000 m.s−1 and also to detect some phases of crack branching during propagation and phases of arrest-re-initiation. Numerical computations, based on X-FEM and combining a local non linear dynamic approach with a RKR type fracture stress criterion, have been performed to depict experimental crack behavior. This paper describes this innovative experimentation and the interpretation by FE calculations and SEM observations associated with quantitative 3D optical microscopy.
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Tarar, Wasim, and M. H. Herman Shen. "A New Hex-8 Finite Element for Gas Turbine Engine Fatigue Life Prediction." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-46389.
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High cycle fatigue is the major governing failure mode in aerospace structures and gas turbine engines. Different design tools are available to predict number of cycles to failure for a component subjected to fatigue loads. An energy-based fatigue life prediction framework was previously developed in recent research for prediction of axial, bending and torsional fatigue life at various stress ratios. The framework for the prediction of fatigue life via energy analysis was based on a new constitutive law, which states the following: the amount of energy required to fracture a material is constant. A 1-D ROD element for unixial fatigue, a BEAM element for bending fatigue and a QUAD-4 element for biaxial fatigue were developed by authors based on this constitutive law. In this study, the energy expressions that construct the new constitutive law are integrated into minimum potential energy formulation to develop a new HEX-8 BRICK finite element for fatigue life prediction. The newly developed HEX-8 BRICK element has 8 nodes and each node has 3 degrees of freedom (DOF) in x, y and z directions. This element is further modified to add the rotational and bending DOFs for application to real world three dimensional (3D) structures and components. HEX-8 BRICK fatigue finite element has capability to predict the number of cycles to failure for 3-D objects subjected to multiaxial stresses. The new HEX-8 element is benchmarked with previously developed uniaxial tension/compression finite element in order to verify the new development. The comparison of finite element method (FEM) results to existing experimental fatigue data, verifies the new finite element development for fatigue life prediction. The final output of this finite element analysis is in the form of number of cycles to failure for each element in ascending or descending order. Therefore, the new finite element framework can predict the number of cycles to failure at each location in gas turbine engine structural components. The new finite element provides a very useful tool for fatigue life prediction in gas turbine engine components as it provides a complete picture of fatiguing process. The performance of the HEX-8 fatigue finite element is demonstrated by comparison of life prediction results for A16061-T6 to previously developed multiaxial fatigue life prediction approach by the authors. Another set of comparison is made to results for type 304 stainless steel data.
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Anago, Joe, Fanrong Kong, Blair Carlson, and Radovan Kovacevic. "A Comprehensive Model for Predicting Fatigue Life of Laser Welded Lap Joint of Galvanized High Strength Steel as a Function of Residual Stresses." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-88318.
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This paper presents a three-dimensional (3D) multi-physics finite element model (FEM) to predict the fatigue life of a laser welded lap joint of dual phase (DP) 980 steel sheets based upon the level of residual stress. A FEM-based thermal analysis is first performed to numerically predict the welding-induced temperature field combined with the corresponding experimental verification. The temperature histories are then loaded into the mechanical model as thermal loading to numerically calculate the evolution curves of thermally induced stress in order to calculate the level of residual stresses after cooling to room temperature. In order to calculate the equivalent fatigue strength in the laser-welded lap joint, the resultant multi-axial stress (including the induced residual stress (RS) result) is loaded into the equivalent uni-axial stress equation via the Sine Method (SM) in order to achieve the stress curve as a function of the loading cycles. A series of fatigue tests of lap joints are also performed in order to achieve the S-N curves, from which an empirical function between the alternating stress and loading cycle is derived in order to predict the fatigue life of the DP980 lap joint. Finally, the maximum fatigue strength can be predicted numerically through the proposed FEM instead of using experimental trials. The numerical results show that a greater temperature gradient and residual stress are mainly located within the fusion zone (FZ) and close to the heat affected zone (HAZ). The residual stress plays an important role in deciding the final fatigue strength and failure of the DP980 lap joint. An X-ray diffraction technique is used to experimentally measure the residual stress distribution within the weld, for which the numerically predicted results exhibit a good agreement. Also, the numerical simulation and experimental measurements of the fatigue life versus the applied load show a good correlation of results.
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Murashov, Iu, N. Obraztsov, N. Kurakina, R. Zhiligotov, and S. Zverev. "Electro-erosion resistance of different electrodes materials for plasma generators." In 8th International Congress on Energy Fluxes and Radiation Effects. Crossref, 2022. http://dx.doi.org/10.56761/efre2022.c3-p-045002.
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The experimental results of the hollow electrodes erosion resistance considering a pilot arc re-ignition during plasma torches operating, are presented in the paper. A high voltage alternating current oscillator is used to simulate an initial process instability. The electrical circuit of the experimental setup with a pulsed discharge current up to 2 kA with time parameter 8/250 and a follow current of 800 A at industrial frequency is described. Four electrodes materials of tungsten (W), iron (Fe), copper (Cu), copper with a sprayed nickel+iron powder (Cu-Ni-Fe) are investigated. X-ray patterns of the different electrode surfaces are demonstrated after 4–9 pulses and one pulse with follow current impacts. The electric charge is calculated by integrating the obtained discharge current to assess the erosion coefficient. The following decreasing order of the electrical erosion resistance is determined: W - Fe - Cu-Ni-Fe - Cu.
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Viveiros, Victor Hugo, Rayanne Lima, Fernando Lucas Martins, Alessandra Coelho, and Matheus Baffa. "Fully-Connected Neural Network for COVID-19 Chest X-Ray Imaging Classification Using Hybrid Features." In Workshop de Visão Computacional. Sociedade Brasileira de Computação - SBC, 2020. http://dx.doi.org/10.5753/wvc.2020.13498.
Full textAbstract:
Discovered on 31st December of 2019, the new Coronavirus has a high transmission capacity and was considered pandemic by the World Health Organization. In only six months is was able to spread all over the world and cause more than 600 thousand deaths. Early diagnosis is essential for governments to take public policies, such as social isolation, commerce control, and contact tracking. In order to make these actions, massive tests are required. On the other hand, diagnosis kits are expensive and not accessible to everyone. Medical imaging, such as thoracic x-ray and Computational Tomography (CT) has been used to visualize the lung and to verify at the first moment the presence of viral pneumonia. However, some countries have few radiologists specializing in chest x-ray analysis. The findings in the image are generally not so easy to see and can easily be confused with traditional pneumonia findings. For this reason, studies in Computer Vision are necessary, both to detect anomalies in imaging and to differentiate the other types of pneumonia. This paper addresses the initial results of a research, which developed an image classification methodology to differentiate x-ray images from sick patients, infected with Coronavirus, and healthy patients. The proposed method, based on the extraction and detection of patterns in texture and color features through a Deep Neural Network, obtained an average accuracy of 95% following a k-fold cross-validation experiment.
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Ahuja, Suresh K. "Visco-Elastic Modulus and Intercalation of Polymer Chains in Epoxy Nano-Composites." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42503.
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Polymer nano-composites (PNC) are polymers which are reinforced with less than 5% by volume of nano-sized particles with high aspect ratios (L/h > 300). Compared to conventional composites, where the reinforcement is on the order of microns, the nano-composites are reinforced on the order of a few nanometers with advantages in processing and toughness. Nano-composites of epoxy clay have been studied where epoxy is mixed at high shear rates with clay. In our method of making nano-composites, an epoxy, Diglycidyl ether of bisphenol (DGEBA) A was mixed under high shear with organically modified mica type silicate (OMTS) either of benzyl dimethyl stearyl ammonium (BDSMA) or of methyl bishydroxyethyl stearyl ammonium chloride ion exchange with sodium montmorillonite. Nano-composites of epoxy cured with hexahydrophthalic anhydride (70%) with polyether polyol (25%) were made also under high shear both at 90C and 120C. Heat of reaction and transition temperature of epoxy nano-composite was compared with cured epoxy nano-composite. Analysis by X-Ray Diffraction was used to determine peaks, spacing and interfacial region. Dynamic visco-elastic measurements were used to distinguish between the nano-composites from two organically modified mica type silicates. Effect of increase in concentration and temperature on visco-elastic modulus of nano-composites was analyzed in terms of intercalation of polymer chains.
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Kaleli, Hakan, and Yves Berthier. "Tribomechanical-Chemical Effects and Visualisation of Additive’s Layer Formation in Engine Crankcase Oil Between Sliding Pairs." In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63509.
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Examination of worn surfaces by optical, electron microscope detection and X-Ray diffraction analysis indicated that the replacement of the pin (steel 52100) by another pin (steel Stub 51115) facilitated and increased the influence of surface degradation which allows the sliding surface to be satisfactorily reactive to form high percentage of protective additive’s layers and to cover uniformly the whole wear track in boundary lubricated conditions. A few minutes of dry test well determined the production of the surface degradation to promote an optimal layer formation. The same type of tests were repeated using pin (sapphire) on the plate (steel Stub 51115) in order to be able to visualize the formation of layers. High speed camera has got images of layers and demonstrates the layer formation during experiment. This study suggests that the surface deterioration is a mechanical process and promotes chemical reactions at solid surfaces. Satisfactory degradation of the surface permits activating lubricant additives to form protective layers. The temperature has a significant chemical influence on the mechanical effect of the material type on the formation of additive’s layer.
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Nakata, Azusa, Philipp Bösl, Fumitoshi Kase, Toru Hashimoto, Shinsuke Shibata, Yann Léost, Ines Butz, et al. "Visualisation of body deformation during collision using X-rays." In FISITA World Congress 2021. FISITA, 2021. http://dx.doi.org/10.46720/f2021-pif-067.
Full textAbstract:
"The passive safety of a vehicle is controlled mainly by passenger restraint systems (seatbelt, airbag, etc.) and body crashworthiness. Currently, while simulation is fully utilized to design a whole vehicle and to predict its performance, conducting actual vehicle collision testing is still necessary to prove vehicle safety performance. Although passenger safety can be confirmed and evaluated dynamically during the collision through many sensors attached to dummies, it is challenging to observe vehicle performance in detail during a collision. Especially with respect to a body-in-white, in spite of its high contribution to the crashworthiness, little information can be obtained from currently existing measuring methods during a collision. Therefore, post-collision measurement is often used to validate crashworthiness performance, however it does not validate dynamic performance directly. This paper introduces an approach to observation of in-crash vehicle body deformation via X-ray. Due to its characteristics to pass through objects, X-ray enables interior observation during a collision. The target object for observation was toeboard deformation under IIHS Small Overlap Offset test, because this part strongly affects leg injuries, but cannot be seen directly during a collision using cameras. A static X-ray experiment was conducted first to optimisze the X-ray setup in order to provideensure maximal visibility of the toeboard. Lead markers were set at each measuring point on the toeboard to enable allocation of these points on the X-ray image. As it was very challenging to conduct the Small Overlap Offset test at the sled facility with a high-speed X-ray system, an alternative test condition, called “reverse Small Overlap Offset” was developed. According to physical laws, it was found that causing a moving barrier to collide with a static vehicle can demonstrate results similar to those of an actual Small Overlap test, if the barrier and the vehicle weights have been adjusted so that energy absorption by the vehicle matches between the two cases. Simulation was used to confirm the validity of the test configuration. Positioning of the X- ray source and detector, as well as design of a running barrier, were also conducted through simulation. The newly designed moving barrier was prototyped and the tests were conducted while only a few X-ray images could be taken due to the limitation of the energy source. Nevertheless, the deformation of the toeboard was able to be observed and measured quantitatively. Traditional post-crash measurement was also conducted to confirm the equivalence of the reverse crash mode to a Small Overlap test. The test result was compared with the simulation result to validate the precision of the simulation. Through the research and the actual test, it was proved that the dynamic observation of body deformation is possible using X-ray technology. With further enhancement of the technology, test results similar to those from the simulation may be observed. The results are also anticipated to contribute to the advancement of simulation technologies, and to the development of a new safety assessment, as they can provide more information on vehicle deformation during the collision process."
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Sharma, Arjun, Tariq S. Khan, Ebrahim Al Hajri, and Md Islam. "Morphological Characterization of Fouling on Air Cooled Fin Fan Heat Exchangers." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66972.
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In today’s fast growing world where availability of energy has become a major concern, the cost of performance demands optimum heat exchange performance over extended periods of operational times. Fouling is one major factor that drastically affects heat exchanger performance. Most of the oil & gas processing plants in the Middle East are located in deserts. Due to scarcity of water most of the installed heat exchangers are air-cooled. These heat exchangers are at high risk of low performance due to dusty/sticky particulate fouling. In order to identify possible active/passive methods to control or ideally eliminate particulate fouling, as a first step, it is desirable to know exact morphology of such particulate fouling. This study presents morphological characterization of selected fouling samples from eight different installed fin fan heat exchangers. The scanning electron microscope (SEM) tests are carried out to determine standard characteristics and size of sample foulant powder. Variability in sizes and shapes is found between samples perhaps due to different working temperature ranges of the selected heat exchangers. The semi quantitative sample composition measured by energy dispersion x-ray micro analysis was as following: 26.50% Si, 26.12% Ca, 10.07% C and 9% Al with traces of Fe, Na, Mg, Cl, and some other salts. X-ray diffraction analysis revealed presence of quartz, calcite and alumina with traces of halite and hematite. The diversity of these fouling samples reflects complexity with respect to their potential removal and effects on heat transfer.
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Matusik, Katarzyna E., Daniel J. Duke, Nicholas Sovis, Andrew B. Swantek, Christopher F. Powell, Raul Payri, Daniel Vaquerizo, Sebastian Giraldo-Valderrama, and Alan L. Kastengren. "A study on the relationship between internal nozzle geometry and injected mass distribution of eight ECN Spray G nozzles." In ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.4766.
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Gasoline direct injection (GDI) nozzles are manufactured to meet geometric specifications with length scales onthe order of a few hundred microns. The machining tolerances of these nominal dimensions are not always knowndue to the difficulty in accurately measuring such small length scales in a nonintrusive fashion. To gain insight intothe variability of the machined dimensions as well as any effects that this variability may have on the fuel spraybehavior, a series of measurements of the internal geometry and fuel mass distribution were performed on a set ofeight nominally duplicate GDI “Spray G” nozzles provided by the Engine Combustion Network. The key dimensionsof each of the eight nozzle holes were measured with micron resolution using full spectrum x-ray tomographicimaging at the 7-BM beamline of the Advanced Photon Source at Argonne National Laboratory. Fuel densitydistributions at 2 mm downstream of the nozzle tips were obtained by performing x-ray radiography measurementsfor many lines of sight. The density measurements reveal nozzle-to-nozzle as well as hole-to-hole density variations.The combination of high-resolution geometry and fuel distribution datasets allows spray phenomena to be linked tospecific geometric characteristics of the nozzle, such as variability in the hole lengths and counterbore diameters,and the hole inlet corner radii. This analysis provides important insight into which geometrical characteristics ofthe nozzles may have the greatest importance in the development of the injected sprays, and to what degreethese geometric variations might account for the total spray variability. The goal of this work is then to further theunderstanding of the relationship between internal nozzle geometry and fuel injection, provide input to improvecomputational models, and ultimately aid in optimizing injector design for higher fuel efficiency and lower emissionsengines.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4766
Reports on the topic "High-order X-FEM"
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Sherman, Amir, Rebecca Grumet, Ron Ophir, Nurit Katzir, and Yiqun Weng. Whole genome approach for genetic analysis in cucumber: Fruit size as a test case. United States Department of Agriculture, December 2013. http://dx.doi.org/10.32747/2013.7594399.bard.
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The Cucurbitaceae family includes a broad array of economically and nutritionally important crop species that are consumed as vegetables, staple starches and desserts. Fruit of these species, and types within species, exhibit extensive diversity as evidenced by variation in size, shape, color, flavor, and others. Fruit size and shape are critical quality determinants that delineate uses and market classes and are key traits under selection in breeding programs. However, the underlying genetic bases for variation in fruit size remain to be determined. A few species the Cucurbitaceae family were sequenced during the time of this project (cucumber was already sequenced when the project started watermelon and melon sequence became available during the project) but functional genomic tools are still missing. This research program had three major goals: 1. Develop whole genome cucumber and melon SNP arrays. 2. Develop and characterize cucumber populations segregating for fruit size. 3. Combine genomic tools, segregating populations, and phenotypic characterization to identify loci associated with fruit size. As suggested by the reviewers the work concentrated mostly in cucumber and not both in cucumber and melon. In order to develop a SNP (single nucleotide polymorphism) array for cucumber, available and newly generated sequence from two cucumber cultivars with extreme differences in shape and size, pickling GY14 and Chinese long 9930, were analyzed for variation (SNPs). A large set of high quality SNPs was discovered between the two parents of the RILs population (GY14 and 9930) and used to design a custom SNP array with 35000 SNPs using Agilent technology. The array was validated using 9930, Gy14 and F1 progeny of the two parents. Several mapping populations were developed for linkage mapping of quantitative trait loci (QTL) for fruit size These includes 145 F3 families and 150 recombinant inbred line (RILs F7 or F8 (Gy14 X 9930) and third population contained 450 F2 plants from a cross between Gy14 and a wild plant from India. The main population that was used in this study is the RILs population of Gy14 X 9930. Phenotypic and morphological analyses of 9930, Gy14, and their segregating F2 and RIL progeny indicated that several, likely independent, factors influence cucumber fruit size and shape, including factors that act both pre-anthesis and post-pollination. These include: amount, rate, duration, and plane of cell division pre- and post-anthesis and orientation of cell expansion. Analysis of F2 and RIL progeny indicated that factors influencing fruit length were largely determined pre-anthesis, while fruit diameter was more strongly influenced by environment and growth factors post-anthesis. These results suggest involvement of multiple genetically segregating factors expected to map independently onto the cucumber genome. Using the SNP array and the phenotypic data two major QTLs for fruit size of cucumber were mapped in very high accuracy (around 300 Kb) with large set of markers that should facilitate identification and cloning of major genes that contribute to fruit size in cucumber. In addition, a highly accurate haplotype map of all RILS was created to allow fine mapping of other traits segregating in this population. A detailed cucumber genetic map with 6000 markers was also established (currently the most detailed genetic map of cucumber). The integration of genetics physiology and genomic approaches in this project yielded new major infrastructure tools that can be used for understanding fruit size and many other traits of importance in cucumber. The SNP array and genetic population with an ultra-fine map can be used for future breeding efforts, high resolution mapping and cloning of traits of interest that segregate in this population. The genetic map that was developed can be used for other breeding efforts in other populations. The study of fruit development that was done during this project will be important in dissecting function of genes that that contribute to the fruit size QTLs. The SNP array can be used as tool for mapping different traits in cucumber. The development of the tools and knowledge will thus promote genetic improvement of cucumber and related cucurbits.